For existing MEMS pressure sensors, regardless of a piezoresistive or capacitive type, a pressure-sensitive film needs to be exposed in air; otherwise, the pressure-sensitive film cannot make a sensitive reaction to external air pressures. Such a pressure-sensitive film is applied generally as an electrical capacitance electrode plate or resistor, and because it must be exposed in air and cannot be disposed in a closed electrical cavity body, external electromagnetic interference will cause an influence on the output of the MEMS pressure sensor.
The existing capacitor-type MEMS pressure sensors mostly adopt a single capacitor detection manner. A pressure-sensitive film and a substrate form a sealed vacuum cavity. When external air pressures are changed, the pressure-sensitive film located above the vacuum cavity is bent. As a result, a capacitance formed by the pressure-sensitive film and the substrate will be changed, and external pressures can be obtained by detecting such capacitance changes.
The above capacitor-type MEMS pressure sensor can detect a change of the external pressures by a single capacitor. Generally speaking, a capacitance variable quantity caused by the change of the external air pressures is very small, and errors of detection carried out by adopting the single capacitor are very large. Besides, except for the external pressure change, other interference signals will also cause the capacitance change. For example, stress, temperature and other common-mode signals all will affect a change value of the capacitance. Detection by the single capacitor cannot filter external interference signals and will influence a noise level of output signals and reduce a signal to noise ratio.
Therefore, there is a demand in the art that a new solution to address at least one of the problems in the prior art.